Combined electrolytic hydrogen gas separator and generator for gas chromatographic systems

ABSTRACT

A COMBINED HYDROGEN GAS SEPARATOR AND GENERATOR DEVICE COMPRISING A PAIR OF THIS PALLADIUM FILM MEMBRANCE ELECTRODES SEPARATED BY AN AQUEOUS HYDROXIDE ELECTRLYTE. ON APPLICATION OF AN ELECTROLYTIC CURRENT TO THE FILMS HEATED TO A TEMPERATURE OF AT LEAST 150*C., HYDROGEN IS SELECTIVELY TRANSFERRED THROUGH THE FIRST FILM. ACROSS THE BODY OF ELECTRLYTE AS PROTONIC HYDROGEN AND IS REGENER-   ATED AS DIATOMIC HYDROGEN ON THE OUTSIDE SURFACE OF THE SECOND FILM. THE IMPURITIES IN THE HYDROGE INLET STREAM COLLECT AT THE OUTSIDE SURFACE OF THE FIRST FIL,. THE CONCENTRATED IMPURITIES CAN BE SENT TO A DETECTOR FOR ANALYSIS. THE REGENERATED HYDROGEN CAN BE RECYCLED TO OPERATE A SEPARATOR UNIT SUCH AS A GAS CHROMATOGRAPHIC COLUMN.

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COMBINED ELECTROLYTIC 3,835,019 AND HYDROGEN GAS lSEPARATOR GENERATORFOR GAS CHROMATOGRAPHIC SYSTEMS Original Filed Feb.

2 SheetSj-Sheet 2 T\wow wow\ wowx L o w w w d..- wow 4|! IH www www Inlw w` www @ow l/ w w www Nov @Ov 'United States Patent O1 iice 3,835,019Patented Sept. 10, 1974 3,835,019 COMBINED ELECTROLYTIC HYDROGEN GASSEPARATOR AND GENERATOR FOR GAS CHROMATOGRAPHIC SYSTEMS James E.Lovelock, Bowerchalke, England, assignor to California Institute ofTechnology, Pasadena, Calif. Original application Feb. 2, 1970, Ser. No.7,922, now Patent No. 3,690,835. Divided and this application Apr. 12,1972, Ser. No. 243,500 Claims priority, application Great Britain, Mar.6, 1969, 12,003/ 69 Int. Cl. C22d 3/02 U.S. Cl. 204-246 10 ClaimsABSTRACT F THE DISCLOSURE A combined hydrogen gas separator andgenerator device comprising a pair of this palladium lm membraneelectrodes separated by an aqueous hydroxide electrolyte. On applicationof Kan electrolytic current to the `films heated to a temperature of at-least 150 C., hydrogen yis selectively transferred through the firstfilm, across the body of electrolyte as protonic hydrogen and isregenerated as diatom'ic hydrogen on the outside surface of the ysecondfilm. The impurities in the hydrogen inlet stream collect at the outsidesurface of the rst lm. The concentrated impurities can be sent to adetector for analysis. The regenerated hydrogen can be recycled tooperate a separator uni-t such as a gas `chromatographic column.

This is a division of application Ser. No. 7,922, filed Feb. 2, 1970 nowPat. No. 3,690,835.

ORIGIN OF THE INVENTION The invention described herein was made in theperformance of work under a NASA contract and is subject to theprovisions of Section 305 of the National Aeronautics and Space Act of1958, `Public Law 85-568 (72 Stat. 435 42 USC 2457).

BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to apparatus and methods for analyzing gas samplesand, more particularly, to a compact and eicient system for analysis ofseparated constituents of micro-sized samples.

2. Description of the Prior Art Analysis of complex samples of matter isgreatly facilitated by gasifying the sample and then passing it ingasifed form through a separation device such as a gas chromatographwhich separates the components of the sample into sequential analyticalcomponents. In a gas chromatograph `and other separation apparatus, gas`or vapor sample to be analyzed is transported through the variousfunctional parts of the apparatus by a stream of inert carrier gas.While this procedure facilitates automation of analysis, it does howeverintroduce other problems.

Thus, sample constituents present in minute quantities are so greatlydiluted by the much larger quantity of carrier gas necessary foroperation of the chromatograph column that they may be diihcult orimpossible to detect. Furthermore, the pressure and flo-w rate of theeluent emerging from the chromatograph may exceed the capability of adetector such as a mass spectrometer.

Various approaches to interfacing a gas chromatograph to a detector havebeen suggested, such as scaling down the dimensions of the chromatographto suit the needs of the detector, interfacing the chromatograph and thedetector with a capillary column or by the use of various plasticmembranes or a fritted glass surface to separate carrier gas beforeintroduction of the eiuent into the detector. None of these approacheshave been entirely satisfactory.

A much improved technique is disclosed in copending applications SerialNo. 852,690 filed Aug. 25, 1969, now Pat. No. 3,638,396; Ser. No.852,825 filed Aug. 25, 1969, now Pat. No. 3,589,171; and Ser. No.852,770 led Aug, 25, 1969 now Pat. No. 3,638,397. In these applicationsthe chromatographic column is interfaced to the detector with a carriergas transfer device such as a palladium tube which is utilized tototally and selectively remove hydrogen carrier gas from the etliuentfrom the chromatographic column. Optionally, a second carrier gas, suchas helium, impermeable to the tube can be introduced at the inlet to thedevice alone or in combination with a controlled amount of hydrogen toprovide a constant flow rate of effluent through the detector.

However, these systems still require the use of heavy carrier gascylinders and essential valving to supply and meter the carrier gas tothe device. Furthermore, the use of high pressure storage cylinders ofcombustible gases such as hydrogen may create hazards to personnel andto the mission of `airborne vehicles carrying such cylinders.

A system is disclosed in Serial No. 852,825 in which it is proposed toseparately generate hydrogen carrier gas by electrolysis of water. Thehydrogen carrier gas is converted to Water by feeding oxygen to thecontainer surrounding the palladium valve tube. This Water is fed to thereservoir of the electrolysis unit which electrolytically decomposes thewater into separate streams of hydrogen and oxygen. Since the functionsof separation and gas generation are physically unrelated and separated,it is diicult to maintain the system in stoichiometric balance and theheat generated by the electrolysis unit must be dissipated and is notutilized for the thermal requirements of the apparatus.

For spacecraft use, and particularly for planetary landers, lbulk andweight limitations and power constraints make it of utmost importancethat the instrumentation provided be compact, of minimal weight andeconomical in its power requirements.

SUMMARY OF THE INVENTION In accordance with the invention, a substantialpower saving and an extremely compact arrangement is effected bycombining the carrier gas separation function with the gas generationfunction in a unitary structure. The arrangement, according to theinvention, utilizes a pair of spaced membranes formed of a materialwhich is selectively permeable to the carrier gas under the conditionsof operation and capable of acting as opposed electrodes.

The membranes are separated by an electrolyte and on application ofelectric potential of suitable polarity between the membranes thecarrier gas is selectively transferred through the wall of the firstmembrane, is transported to the second membrane and is regeneratedtherethrough as pure carrier gas. The gas output from the rst side ofthe membrane will contain concentrated sample which can be sent to adetector while the output of pure carrier gas from the second membranecan -be recycled to a separation device such as a gas chromatographcolumn. The output from the column is returned to the first side of thefirst membrane for separation of carrier gas preliminary to detection ofsample.

These and many other attendant advantages of the invention will becomeapparent as the invention becomes better understood by reference to 4thefollowing detailed description when considered in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a firstembodiment of an analysis system according to the invention;

FIG. 2 isa further embodiment of a closed cycle analysis systemaccording to the invention;

XFIG, 3 is a sectional view of a further embodiment of a combined gastransfer and generator device; and

FIG. 4 is a further schematic view of a combined gas generator andseparator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of ananalytical system according to the invention as illustrated in FIG. 1generally includes a chromatographic column 12, a combined carrier gas'transfer and generator device -14 and a detect-or 16. Sample isintroduced to the inlet 18 tothe column 12 through a 'sample inlet 20containing a valve 22.

The column 12 consists of a series of reactants which segregate the gassample by affecting the rate at which the different constituents of thegas sample iiow through the column to provide an eiuent containing asequential passage of the components. As the sample is introducedthrough the sample introduction valve 22 'it is mixed with a firstcarrier gas which is introduced into the inlet 18 at `a constantpressure and flow rate from recycle conduit 24. The mixture of firstcarrier gas and sample leaves the column through an outlet 26 whichcommunicates with the inlet 28 to the device 14.

The device 14 comprises an outer cylindr'ical casing 30 closed bycylindrical electrical insulator end plates 32. The end plates 32support a set of coaxial cylinders comprising an inner tubular anodemembrane 34 which is surrounded by an outer tubular cathode membrane 36.The annular space between the anode 34 and cathode 36 is filled with anelectrolyte 38 capable of transporting an ionic species of the ifirstcarrier gas under the conditions of operation. The outer chamber 40between `the casing 30 and the cathode 36 serves as a collection chamberfor first carrier gas as will be described.

Electrical leads 42 are connected to the anode 34 and cathode 36 and toan electrolysis power source and controller 44. An insulated heatingcoil 46 may be placed -in thermal contact with the outer casing 30. Theends of the coil 46 4are connected 'through electrical leads 48 to aheater power source and controller 50.

The first carrier gas maybe hydrogen of high purity and the transferdevice may then comprise a thin film of conductive material selectivelypermeable to hydrogen. Palladium and its alloys are remarkably permeableto hydrogen as long as the film is maintained at a temperature aboveabout 100 C. to 150 C. The film is suitably maintained at temperaturesbelow 600 C. -to avoid unnecessary rearrangement of components subjectto catalytic hydrogenation or rearrangement in the presence of heatedpalladium.

Pure palladium when subject to temperature cycling in the presence ofhydrogen, suffers mechanical distortions. However, an alloy of palladiumcontaining to 30% silver, preferably about silver is as permeable tohydrogen and is mechanically stable. Other palladium alloys, forexample, palladium-rhodium alloys may confer more resistance tocorrosion to the films and extend the useful life of thegenerator-separator. The palladium tube may be provided in variousconfigurations and lengths of tubing may be connected in parallel toprovide increased surface area with less flow resistance. Membranes ortubes can also he formed from a base structural material such yas a.porous ceramic coated with a thin film of palladium or a suitablehydrogen permeable palladium alloy.

The hydrogen iiux fora given hydrogen pressure difference through a thinililm of palladium or alloy is dependent on tube geometry, wallthickness and wall temperature. The flux of hydrogen through -the wallof a palladium-25 silver alloy Atube having an internal diameter of0.0152 centimeter and a wall thickness of 0.0076 centimeter and a lengthof 25 centimeter varies with temperature as the tube is heated in airfrom 0.2 ml. sec.-1 vat 200 C. to 0.45 ml. sec.1 at 450 C. Furtherexperiments have demonstrated that it is possible to maintain an activeopen barrier between hydrogen -gas at ambient pressure and -a hardvacuum with the use of the hydrogen gas separator transfer deviceutilizing heated palladium tilms.

To maintain the palladium film at a temperature at which yit ispermeable to hydrogen the cell may be heated by various means such as bydisposing it in an oven or by heating the device electrically. Forexample, the heating coil 46 may be utilized to raise the tubes 34 and36 and the electrolyte 38 to a temperature above 200 C. Though it isdesirable -to maintain the resistance of the electrodes and electrolyte-as low as possible for purposes of electrical power efiiciency, theelectrolytic ce'll may in some con- `figur-ations provide a sufiicientviu-ternal impedance to produce the desired heating on pa'sage ofcurrent through the electrodes and electrolyte. In other configurations,the heat supplied by operation of the electrolytic cell contributes tothe heat received to maintain the films at the desired temperature.Thus, -the electrolysis current supplied by the electrolysis power andcontroller funit 44 may also be utilized to provide a portion of thenecessary heating.

Removal of hydrogen at currents higher than a limiting value results -inhydrogen generation at the cathode greater than hydrogen separationthrough the anode. The controller 44 should be set a current lower thanthe limiting value to maintain the electrolytic cell in stoichiome-tricbalance. At a given temperature and current, the hydrogen removalcapacity is fairly constant. By providing lau excess hydrogen ow throughthe interior of -the anode tube 34, a low controlled residual flow ofhydrogen mixed with the sample leaves the device 14 through the outlet52.

When operated in the mode resulting in complete removal of carrier gas,the propulsive means needed 1to convey the enriched, segregated sampleconstituent through the detector 16 may be eliminated. This could resultin recombination of segregated sample constituents. In this mode ofoperation it -is preferable to introduce a second carrier gas to theinlet 28 to the device 14 from supply cylinder 54 containing aregulating valve head 56. The second carrier gas enters the system at apoint after the column 12 but before the devi-ce 14. The tubularmembranes 34 and 36 are selected to be permeable to the first carriergas but not to any other gas so that as the mixed carrier stream passes-through lthe device 14 the rst carrier gas is eliminated through theWalls of the device and the sample components are left suspended in thesecond carrier or scavenge gas. The concentrated stream is then sweptinto the detector 16. A suitable second carrier gas is helium. Furthercontrol of the flow rate of helium may be provided by diluting thehelium with rst carrier gas as disclosed in co-pending application Ser.No, 852,770, now Pat. No. 3,638,397.

However, in accordance with the invention, it is possible to dispensewith the second carrier lgas supply.

This is accomplished by supplying excess hydrogen to the System cell insuch a manner that hydrogen separation capacity is not suicient tototally remove the hydrogen carrier gas. Thus, a controlled, smallresidual flow of hydrogen gas could be utilized to sweep the segregatedconstituents through the detector.

The electrolyte is a material capable of transporting an ionic speciesof the carrier gas from one electrode to the other, is inert withrespect to the electrodes, is stable at the temperature of operation andis capable of regenerating the carrier gas by electrolytic associationor disassociation as is required. The electrolyte may be an acid, basicor salt material and is preferably an inorganic metal hydroxide.

The most suitable material for use in the invention are the Group Imetal hydroxides such as sodium hydroxide, potassium hydroxide, orlithium hydroxide. The hydroxides should be utilized in a hydrated form,preferably contain to 35% water of hydration since this both lowers thepower requirement and the temperature at which the electrolyte becomesmolten. Improved operation of the cell occurs when at least 10 to 25%`of the lighter weight lithium hydroxide is mixed with sodium orpotassium hydroxide, preferably the latter. Commercial potassiumhydroxide containing 25% water melts at 275 C. The addition of 10%lithium hydroxide to this electrolyte further lowers the temperature atwhich the electrolyte becomes molten to about 200 C.

The coaxial anode 34 and cathode 36 having molten aqueous electrolytedisposed therebetween acts as an electrolytic cell for thedisassociation of water. Diatomic hydrogen gas contacting the insidesurface 60 of the anode tube 34 will disassociate and be transportedthrough the tube wall as protonic hydrogen, H+. At the outside surface62 of the anode tube 34 the hydrogen protons combine with hydroxyl ion,O1I- to form water. The water is transported through the electrolyte 38to the inside suface 64 of the cathode tube 36. At the surface 36 thewater is electrolytically disassociated into hydroxyl ions and protons.The hydrogen protons transfer through the tube wall 36.

On the outside surface 66 of the cathode tube 36 the hydrogen protonsrecombine to form diatomic hydrogen, H2, the diatomic hydrogen collectsin the collection chamber 40. Under the applied electrolytic potential,hydrogen can build up in chamber 40 to a pressure as high asapproximately 700 p.s.i. which drives the hydrogen through the recycletube 24 to the junction with the sample inlet 18 of the gaschromatographic system 12. The mixed gasified sample is then sweptthrough the column 12 by the recycle hydrogen.

After passage through the column 12, the gas mixture emerges throughoutlet 26 and enters the inlet 28 to the device 14. It the temperatfureof the wall of tube 34 is below the critical diffusion level, the entiregas mixture including the hydrogen carrier gas will enter detector 16.However, if the temperature of tube 34 exceeds a temperature of about150 C., the hydrogen in the mixture will diffuse through the wall oftube 34 and be removed from the sample stream.

Control of the temperature of the tube wall, the electrical potential ofthe cell and the amount of excess hydrogen in the system makes itpossible to control the amount of hydrogen removed from the mixture.Since this control can now be effected electrically, mechanical valvingand a source of secondary carrier gas becomes unnecessary. Furthermore,the molten electrolyte provides a supply of hydroxyl ions which acts asa driving force to increase the flow of hydrogen through the wall ofanode tube 34 and this further obviates the need to carry a supply ofoxygen previously disclosed to act as a driving force for hydrogenremoval as disclosed in the above referenced co-pending applications.Since the temperature of the molten electrolyte and the electricalpotential applied to the cell also affect cathode tube 36 in the samemanner, it is apparent that the amount of gas evolved into thecollection chamber 40 will be at a proportional rate, thus balancingcarrier gas separation with carrier gas generation.

The ionic and water content of the electrolyte is also maintainedconstant during operation. The OH'- ion which is liberated ondecomposition of water as the cathode recombines with the H+ ionsentering the system to form water which maintains the hydrationconcentration of the electrolytic cell constant. For this reason it ispreferred to maintain an excess of hydrogen protons in the system at alltimes to prevent the formation of molecular oxygen which will causebubbles in the electrolyte and excessive pressure on the thin wallelectrode tubes.

The fused electrolyte utilized, must be Very pure to provide continuoustrouble free operation. The initial supply of hydrogen carrier gasshould also be pure to avoid analytical error. It is important tomaintain the temperature of the Ianode tube above the critical diffusiontemperature so that a sufficient supply of hydrogen is maintained in theelectrolyte at all times. It is also desirable that the tube beactivated prior to assembling the cell and is preferable that metalsother than palladium, silver or gold not be present in the cell.

Trace quantities of other metals such as formed from brazed connectionswould provide nuclei about which hydrogen could evolve. This Iwill beevidenced by the presence of hydrogen bubbles within the mass of theelectrolyte. It is desirable that the hydrogen be generated only at thecathode wall for most efficient diffusion through the palladiummembrane. Further assurance of prevention of oxygen generation can beprovided by priming the system with free hydrogen before startup so thathydroxyl ions are favored and any oxygen present in the system can berecombined immediately. When the cell is operating properly there shouldbe no bubbling or change in composition of the electrolyte.

A combined transfer-generator device was constructed utilizing 1/16thinch, 0.005 inch wall palladium-25 silver alloy tubing for the anode and0.02 inch OD, 0.005 inch wall palladium-25 silver alloy tubing for thecoaxial cathode. The electrolyte was a 10% lithium hydroxidepotassiumhydroxide (25% water) mixture. The efficiency of this configuration wasexcellent. Only 30 to 70 millivolts of potential were required togenerate a given quantity of hydrogen for use as a Carrier gas comparedto 1550 millivolts when hydrogen was not flowing in the separatorportion of the device. The power needed to produce hydrogen can be atleast 10l times less than that required by the usual methods ofelectrolytic decomposition of water.

The device could deliver 6.6 ml. per minute and completely remove itagain. The hydrogen flow can be removed through the device within 2seconds of the receipt of a signal by raising the potential applied tothe anode lwhich is immersed in molten alkali at 240 C. The flow risesfrom 0 to 6.6 ml. per minute in 2.4 seconds. The overall configurationis very compact and the heat provided by the electrolytic cell maintainsthe electrolyte molten, raises the tubes to the minimum criticaldiifusion temperature and the leakage heat from the cell can also beutilized to heat the chromatographic column to improve its operation.

The detector 16 may be a conventional colligative property sensorutilized in gas chromatographic systems such as a thermal conductivity,ionization cross-section or gasdensity balance detector which determinesthe identity and amount of each segregated constituent flowing from thecolumn. These detectors usually operate at atmospherie pressure and haveno means of pumping sample through the detector. Therefore, to maintainthe system closed and in stoichiometric balance, it is preferred tooperate the system with a supply of secondary carrier gas from cylinder54, and with the carrier gas transfer-generator device 14 operating atmaximum hydrogen removal efficiency. With a detector such as a massspectrometer having its own source of vacuum for introducing sample intothe detector, the system need not be operated with a source of secondarycarrier gas.

With the combined hydrogen transfer-generator device, according to theinvention, the quantity of hydrogen removed can exactly equal thatgenerated. In a closed system the metered carrier gas can in sucharrangement be the excess hydrogen in the system. The excess hydrogengas can conveniently be fully regenerated in a small additionalgenerator-separator device. The excess hydrogen gas will leave the rstgenerator-separator at a controlled flow rate.

Referring now to FIG. 2, a closed cycle analysis system incorporatingboth a conventional gas chromatographic column detector and a massspectrometer is illustrated. The system includes a column 212, a firstcoaxial carrier gas transfer-generator device 214, a detector 216, asecond carrier gas transfer-generator device 218, and a massspectrometer 220.

A vapor sample such as that derived from a pyrolysis unit, not shown, isintroduced through sample inlet 210 containing a valve 222 to the inlet223 of the column 212. The sample mixes with hydrogen gas beinggenerated and collected in chamber 224, of the device 214. The mixedcarrier gas-sample stream flows through the column 212 and enters theinlet 228 of the device 214. At the inlet 228 the mixed carrier gasstream merges with the hydrogen being recycled from the second device218 through conduit 219.

'I'he power source 244 is set at a level to provide a constant meteredflow of hydrogen leaving the outlet 252 of the device 214. As the gasesow through anode tube 236, substantially all the hydrogen will betransferred through anode tube 236, electrolyte 238 and cathode tube 240such that the transferred hydrogen collects in chamber 224 and operatesthe column 212. The remaining excess hydrogen leaves the device throughoutlet 252 and carries the sample through the detector 216. The outputfrom the detector 216 ows through outlet 250 into the inlet 260 to thesecondary transfer-generator device 218. The secondary power source andcontroller 262 supplies suicient current and heat to transfer all of thesecondary hydrogen through the anode 264, molten electrolyte 266 andcoaxial outer cathode 268 such that the hydrogen collects in the outerchamber 270. The collected hydrogen is transferred through tube 219 backto the first transfer device 214 as previously explained. The remainingsample is drawn through outlet pipe 272 into the mass spectrometer 220.

The analysis apparatus of FIG. 2 can be operated without a massspectrometer in which case the sample exiting through tube 272 cansimply be exhausted from the system. Since the transfer-generator deviceof the invention can totally remove hydrogen from the system, by simplyvarying the ratio of the power being applied by tlhe power source andcontrollers 244 and 262, the ilow rate through the detector 216 can bevaried.

Another configuration of the structure of the electrolytic cell isillustrated in FIG. 3. In FIG. 3, the combined carrier gastransfer-generator device 314 comprises a container 300 having a lid 302formed of an electrically insulating material which is stable at thetemperature of operation of the cell. A body of electroly-te 338 isreceived within the container 300. An anode 334 and a cathode 336penetrate the lid 302 and have portions immersed rwithin the body ofelectrolyte 338.

The anode 334 is in the form of a thin wall tube, suitably fabricated ofa palladium-silver alloy having an open input end 316 and an open outputend 318. The cathode 336 is in the form of a thin wall tube having aclosed end 320 immersed within the electrolyte 338 and an open end- 322extending from the device. Electrical leads 324 are connected to theanode 334 and cathode 336 and to a variable power source and controller,not shown.

In the operation of the device of FIG. 3, an impure hydrogen stream isfed into the inlet 316 to the cathode tube 334 and the controller is setto maintain the temperature of the system above about 200 C. The body ofelectrolyte 338 melts under these conditions and hydrogen diffusesthrough the walls of tube 334 across the body of electrolyte 338separating Ithe anode 334 and cathode 336 and traverses the wall of thecathode 336. The hydrogen leaves the device 314 through the cathodeoutlet 322. The impurities present in the hydrogen stream exit as aconcentrated stream through the anode outlet 318. The combinedtransfer-generator device can be used in a closed cycle system asillustrated above or may be used to concentrate or recover selectedimpurities or to purify hydrogen.

A further version of the combined transfer-generator device isillustrated in FIG. 4. In the embodiment of FIG. 4, the compartment 400for the electrolyte 438 is formed o't two side walls of thin sheets ofpalladium-silver alloy and the end walls 402 are formed of electricinsulating material. The side walls are connected by electric lea-ds 404to a lvariable power source and controller, not shown. When the sidewalls are connected in the polarity illustrated, the left hand wallfunctions as an anode 434 and the right hand wall functions as a cathode436.

A flow-through chamber 432 is formed adjacent the outside surface 406 ofthe anode 434, the anode forming one wall of the chamber 432. Thechamber has an inlet 408 and an outlet 410. A collection chamber 412 isformed adjacent the outside surface 414 of the cathode 438. The cathode438 forms one wall of the chamber 412. The chamber 438 is provided witha gas outlet 416.

The impure hydrogen stream or hydrogen carrier gas containing a minoramount of vaporous sample to be separated is introduced into inlet 408.The power source and controller is set to a level Ato melt theelectrolyte and to heat the electrode palladium lrns 434 and 436 to atemperature of at least 200 C. The hydrogen in the inlet streamtraverses anode lm 434, .is transported through the electrolyte to thecathode lm 436 and traverses the cathode and collects in collectionchamber 412. Pure hydrogen is removed through outlet 416. The impuritiesor vaporous sample collect in chamber 432 andare removed through outlet410.

An extremely compact arrangement is elfected according to the inventionby combining a hydrogen gas transfer device with a hydrogen generatorlin a unitary structure. The power requirement is substantially reducedand the waste heat provided by the electrolysis is utilized to maintainthe walls of the palladium separator at operating temperature. Theextremely eicient separation of hydrogen provided by the device resultsin a marked gain in sensitivity and more accurate analysis. The devicecan be effectively coupled with an ambient pressure detector and/or witha detector operating under high vacuum such as a mass spectrometer.

Since the temperature of the molten electrolyte can be chosen to becompatible with that required by the palladium membranes for hydrogendiffusion, only a single source of heat is required to operate both thegenerator and the separator. Further, since the electrolysis current mayalso be used as the heating current in some circumstances only a singlesource of power is required.

The combined transfer-generator device of the invention makes possiblethe construction of an extremely compact, portable gas chromatograph orgas chromatographmass spectrometer system since the device supplies itsown source of pure hydrogen carrier gas for operating both the columnand the mass spectrometer. The flow rate of the carrier gas can becontrolled at a programmed variable rate without resorting to the use ofvalves or other mechanical aids. This control is effected simply byappropriate choice of the geometry and capacity of thegenerator-separator and by controlling the electrical power supplied tothe electrodes. In a portable apparatus there .is a savings in bulkweight .and power requirements and the hazards associated with the useof high pressure storage cylinders are avoided.

The hydrogen transfer-generator devices makes possible the long soughtgoal of a twenty pound combined gas chromatographic-mass spectrometersystem for planetary missions where data on composition of planetarysoils and atmospheres is being sought. The device will also nd useaboard satellites and other aerospace vehicles for analysis ofatmosphere and especially in smog control. The device will findcommercial application whenever a very lightweight gas chromatograph isrequired for gas or vapor analysis.

It is to be realized that only preferred embodiments of the inven-tionhave been disclosed and that numerous substitutions, alterations andmodifications are all permissible without departing from the spirit andscope of the invention as defined in the following claims.

What is claimed is:

1. A combined, electrolytic, hydrogen gas separatorgenerator devicecomprising:

a first palladium electrode film impermeable to gases lat a temperatureno more than a first temperature and selectively permeable to hydrogengas at a temperature above the first temperature and having a first andsecond surface;

a -second palladium electrode film impermeable to gases at a temperatureno more Ithan a first temperature and selectively permeable to hydrogengas at a temperature above the first temperature and having a first andsecond surface;

chamber means including a pair of spaced insulators defining a closedchamber between said first surfaces;

a body of electrolyte molten at said first temperature received in saidchamber in contact with said first surfaces and capable ofelectrolytically transporting hydrogen gas between said first surfaces;

first compartment means enclosing said second suface of the firstelectrode;

inlet means for supplying a gas stream containing irnpurity gas and aportion of hydrogen g-as to the first compartment;

first outlet means for removing said impurity gas from the firstcompartment;

second compartment means enclosing the second surface of the secondelectrode for collecting hydrogen gas;

second outlet means for removing hydrogen gas from Ithe secondcompartment;

contact means -applied to each electrode for impressing an electricpotential across said electrodes and electrolyte to form an electrolyticcell;

heating means for heating said electrode films to said first temperatureto render said films selectively permeable to hydrogen gas; and

potential source means connected to said electrodes so as to transferhydrogen through said first electrode, across said electrolyte, throughsaid second electrode and collect in said second compartment.

2. A device according to Claim 1 in which the films comprise 1an alloyof palladium and silver.

3. A device according to Claim 2 in which Ithe electrode films are inthe form of tubes.

4. A device according to Claim 3 in which `the tubes have a portionimmersed in the body of the electrolyte and a portion extendingtherefrom.

5. A device according Ato Claim 3 wherein said tubes are of ldifferentdiameters and further include a pair of insulating end memberssupporting said tubes in av coaxial configuration defining an annularchamber for receiving said electrolyte.

6. A device according to Claim 5 in which said electrolyte is molten atthe operating condition of the device.

7. A device according to Claim 6 in which the electrolyte is aninorganic hydroxide.

8. A device according to Claim 7 in which the electrolyte is a Group Imetal hydroxide.

9. A device according `to Claim 8 in which the electrolyte contains upto 10% of lithium hydroxide.

10. A device according to Claim 8 in which the electrolyte contains l0to 35% water.

References Cited UNITED STATES PATENTS 3,180,762 4/1965 Oswin l36863,148,089 9/1964 Oswin 136-86 3,489,670 l/l970 Maget 204-129 3,448,0356/1969 Serfass 204-272 3,188,283 6/1965 Cole 204-277 JOHN H. MACK,Primary Examiner W. I. SOLOMON, Assistant Examiner U.S. Cl. X.R.

-158; 204-60, 129, 247, 272, 274, DIG 3

